# US 7,612,758 B2 · Brightness control method and device for a display

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- Number: US 7,612,758 B2
- Document ID: US7612758B2
- Status: Granted
- Kind: B2
- Application number: 11/311,320
- Filed: 2005-12-20
- Published: 2006-10-26
- Granted: 2009-11-03
- Earliest claimed: 2005-04-21
- Assignees: Sunplus Technology Co., Ltd.
- Inventors: Ho-Hsing Yang
- Web page: https://patentgrep.com/patent/US7612758B2

## CPC

- G09G 3/3406: {Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336)}
- G09G 2320/064: by time modulation of the brightness of the illumination source
- G09G 2320/0646: Modulation of illumination source brightness and image signal correlated to each other
- G09G 2320/0653: Controlling or limiting the speed of brightness adjustment of the illumination source
- G09G 2320/066: for control of contrast
- G09G 2330/021: Power management, e.g. power saving
- G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

A brightness control method and device for a display, which calculates a brightness distribution of partial frame image, determines when the partial frame image tends to be dark or light, compares a backlight brightness of the display with a predetermined value in accordance with the partial frame image determined, and accordingly adjusts the backlight brightness of the display.

## Claims

### Claim 1

A brightness control device for a display, comprising:
a video stream histogram unit, which receives a partial frame image and calculates a brightness distribution of the partial frame image;
a dynamic range calculation module, which determines a brightness of the partial frame image in accordance with the brightness distribution, and determines if a backlight brightness of the display meets with the brightness of the partial frame image in order to generate a control signal, wherein the backlight brightness is reduced when the brightness distribution of the partial frame image tends to be dark and the backlight brightness is greater than a third predetermined value, or the backlight brightness is increased when the brightness distribution of the partial frame image tends to be light and the backlight brightness is smaller than a fourth predetermined value; and
a backlight pulse width modulation (PWM) controller, which adjusts the backlight brightness of the display in accordance with the control signal.

### Claim 2 (depends on 1)

The device as claimed in claim 1, wherein the partial frame image is a plurality of pixels or a segment of the frame.

### Claim 3 (depends on 1)

The device as claimed in claim 1, wherein the video stream histogram unit calculates a quantity of dark dots of the partial frame image or a quantity of light dots of the partial frame image.

### Claim 4 (depends on 1)

The device as claimed in claim 1, wherein the video stream histogram unit finds a respective maximum value among RGB values of each pixel from the partial frame image and further compares the respective maximum value with a first predetermined value.

### Claim 5 (depends on 1)

The device as claimed in claim 1, further comprising:
a digital to analog converter connected to the backlight PWM controller for converting a digital backlight pulse width modulation signal which is outputted from the backlight PWM controller to an analog backlight pulse width modulation signal.

### Claim 6 (depends on 5)

The device as claimed in claim 5, further comprising:
a contrast enhancer, connected to the video stream histogram unit and the dynamic range calculation module, for rescaling amplitude of each pixel of the partial frame image to improve contrast of each pixel.